In the field of medical technology, various apparatuses are known with which fluid can be withdrawn from patients or fluids can be fed to patients via a hose line. The access to the patient generally takes place with a catheter for introduction into body organs or a cannula for the puncturing of vessels. During the examination or treatment, a correct access to the patient must be ensured. It is therefore necessary to monitor the patient access. A correct access to the patient is required in particular by extracorporeal blood treatment apparatuses comprising an extracorporeal blood circuit.
Devices for monitoring a vascular access are known, which comprise a moisture sensor in order to be able to detect the issuing of blood at the puncture point. The known moisture sensors are constituted as a pad which is to be placed on the puncture point. International Patent Publication No. WO 2006/008866 A1, U.S. Patent Publication No. US 2005/0038325 A1 and U.S. Pat. No. 6,445,304 describe moisture sensors comprising an absorbent material in which an electrically conductive structure is embedded. The detection of moisture is based on the measurement of the electrical resistance between the strip conductors.
International Patent Publication No. WO 2009/075592 A2 describes a moisture sensor in the form of a strip of woven fabric on which or in which two parallel strip conductors are provided, between which the electrical resistance is measured. The two strip conductors are formed by conductive yarns which run only in the longitudinal direction of the strip of woven fabric. Electrical contact points between intersecting strip conductors are not provided.